MCQ Questions for Class 12 Chemistry Chapter 3 Electrochemistry with Answers

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Electrochemistry Class 12 MCQs Questions with Answers

Question 1.
Standard solution of KNO3 is used to make a salt bridge because
(a) Velocity of K+ is greater than that of NO\(_{3}^{-}\).
(b) Velocity of NO\(_{3}^{-}\) is greater than that of K+.
(c) Velocity of both K+ and NO\(_{3}^{-}\) are nearly same
(d) KNO3 is highly soluble in water.

Answer

Answer: (c) Velocity of both K+ and NO\(_{3}^{-}\) are nearly same


Question 2.
For the electro-chemical cell:
M| M+|| X| X, E\(_{M^+, M}^{0}\) = 0.44 V and E\(_{x, x^-}^{0}\) = 0.33 V
From the data one can deduce that
(a) M+ X → M+ + X is the spontaneous change
(b) M+ + X → M + X is the spontaneous reaction
(c) Ecell = 0.77 V
(d) Ecell = -0.77 V

Answer

Answer: (b) M+ + X → M + X is the spontaneous reaction


Question 3.
Galvanised iron sheets are coated with
(a) Carbon
(b) Copper
(c) Zinc
(d) Nickel

Answer

Answer: (c) Zinc


Question 4.
How many coulombs are required for the oxidation of 1 mole of H2O to O2?
(a) 1.93 × 105 C
(b) 9.65 × 104 C
(c) 3.86 × 105 C
(d) 4.825 × 105 C

Answer

Answer: (a) 1.93 × 105/sup> C


Question 5.
Rust is a mixture of
(a) FeO and Fe (OH)3
(b) FeO and Fe (OH)2
(c) Fe2O3 and Fe (OH)3
(d) Fe3O4 and Fe (OH)3

Answer

Answer: (c) Fe2O3 and Fe (OH)3


Question 6.
The Standard electrode potentials for the half cell reactions are as follows
Zn ? Zn2+ + 2e [E° = 0.41 V]
Fe ? Fe2+ + 2e [E° = 0.76 V]
(a) -0.35 V
(b) 0.35 V
(c) + 1.17 V
(d) -1.17 V

Answer

Answer: (b) 0.35 V


Question 7.
Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox titration. Some half cell reactions and their standard potentials are given below:
MNO4 (aq) + 8H+ (aq) + 5e → Mn2+ (aq) + 4H2O (1) E° = 1.51 V
Cr2O72- (aq) + 14H+ (aq) + 6e → 2 Cr3+ (aq) + 7H2O (1) E° = 1.38 V
Fe3+- (aq) + e ? Fe2+ (aq) E° = 0.77 V
Cl2 (g) + 2e ? 2Cl (aq) E° = 1.40 V
Identify the only incorrect statement regarding the quantitative estimation of aqueous Fe (NO3)2.
(a) MnO\(_{4}^{-}\) can be used in aqueous HCl.
(b) Cr2O\(_{7}^{2-}\) can be used in aqueous HCl.
(c) MnO\(_{4}^{-}\) can be used in aqueous H2SO4.
(d) Cr2O\(_{7}^{2-}\) can be used in aqueous H2SO4.

Answer

Answer: (a) MnO\(_{4}^{-}\) can be used in aqueous HCl.


Question 8.
The standard reduction potentials of Cu2+/Cu and Cu2+/Cu+ are 0.337 and 0.153 respectively. The standard electrode potential of Cu+/Cu half cell is
(a) 0.184 V
(b) 0.827 V
(c) 0.521V
(d) 0.490 V

Answer

Answer: (c) 0.521V


Question 9.
The standard reduction potentials of X, Y, Z metals are 0.52, -3.03, -1.18 respectively. The order of reducing power of the corresponding metals is:
(a) Y > Z > X
(b) X > Y > Z
(c) Z > Y > X
(d) Z > X > Y

Answer

Answer: (a) Y > Z > X


Question 10.
Which of the following is not a good conductor?
(a) Cu
(b) NaCl (aq)
(c) NaCl (molten)
(d) NaCl(s)

Answer

Answer: (d) NaCl(s)


Question 11.
The e.m.f. of the cell Zn/Zn2+ (0.01 M) || Fe2+ (0.001 M) Fe at 298 K is 0.2905 volt. Then the value of equilibrium constant for the cell reaction is:
(a) e0.32/0.0295
(b) 100.32/0.0295
(c) 100.26/0.0295
(d) 100.32/0.0591

Answer

Answer: (b) 100.32/0.0295


Question 12.
The volume of H2 gas at NTP obtained by passing 4 amperes through acidified H+O for 30 minutes is:
(a) 0.0836 L
(b) 0.0432 L
(c) 0.1672 L
(d) 0.836 L

Answer

Answer: (a) 0.0836 L


Question 13.
4.5 g of aluminium (at. mass 27 amu) is deposited at cathode from Al3+ solution by a certain quantity of electric charge. The volume of hydrogen produced at STP from H+ ions in solution by the same quantity of electric charge will be:
(a) 44.8 L
(b) 11.2 L
(c) 22.4 L
(d) 5.6 L

Answer

Answer: (a) 44.8 L


Question 14.
For a spontaneous reaction, ?G, equilibrium constant K and E\(_{cell}^{0}\) will be respectively.
(a) – ve > 1, + ve
(b) + ve > 1 – ve
(c) -ve, < 1, -ve
(d) -ve, > 1, -ve

Answer

Answer: (a) – ve > 1, + ve


Question 15.
The amount of electricity required to deposit 1 mol of aluminium from a solution of AlCl3 will be
(a) 0.33 F
(b) 1 F
(c) 3 F
(d) 1 ampere

Answer

Answer: (c) 3 F


Question 16.
A current of 2.0 A passed for 5 hours through a molten metal salt deposits 22.2 g of metal (at. wt. = 177). The oxidation state of the metal in the metal salt is
(a) +1
(b) +2
(c) +3
(d) +4

Answer

Answer: (c) +3


Question 17.
Standard electrode potentials are Fe2+/Fe, E° = – 0.44; Fe3+/Fe2+, E° = 0.77 V. Fe2+, Fe3+ and Fe blocks are kept together then
(a) Fe3+ increases
(b) Fe3+ decreases
(c) Fe2+/Fe3+ remains unchanged
(d) Fe2+ decreases?

Answer

Answer: (b) Fe3+ decreases


Question 18.
Ionic mobility of Ag+ ions [?Ag+ = 5 × 10-4 ohm-1 cm² eq-1] is
(a) 5.2 × 10-9
(b) 2.4 × 10-9
(c) 1.52 × 10-9
(d) 8.25 × 10-9

Answer

Answer: (a) 5.2 × 10-9


Question 19.
On the basis of information available from the reaction.
4/3 Al + O2 ? 2/3 Al2O3, ?G = – 827 kj mol-1 of O2 the minimum emf required to carry out the electrolysis of Al2O3 is
(a) 2.14 V
(b) 4.28 V
(c) 6.42V
(d) 8.56V

Answer

Answer: (a) 2.14 V


Question 20.
The E\(_{M^{3+}/M^{2+}}^{0}\) values for Cr, Mn, Fe and Co are -0.41, + 1.57, + 0.77 and +1.97 V respectively. For which one of the metals, the change in oxidation state from +2 to +3 is easiest?
(a) Cr
(b) Mn
(c) Fe
(d) Co

Answer

Answer: (a) Cr


Question 21.
For a cell reaction involving two electron change the standard emf of the cell is found to be 0.295 V at 25°C. The equilibrium constant for the reaction at 25°C will be:
(a) 2.95 × 10²
(b) 10
(c) 1 × 1010
(d) 1 × 10-10

Answer

Answer: (c) 1 × 1010


Question 22.
If Zn2+/Zn electrode is diluted 100 times, then the change in emf is
(a) increase of 59 mV
(b) decrease of 59 mV
(c) increase of 29.5 mV
(d) decrease of 29.5 mV.

Answer

Answer: (b) decrease of 59 mV


Question 23.
If the equivalent conductance of 1 M benzoic acid is 12.8 ohm-1 cm² and if the conductance of benzoate ion and H+ ion are 42 and 288.42 ohm-1 cm² respectively, its degree of dissociation is:
(a) 39%
(b) 3.9%
(c) 0.35%
(d) 0.039%

Answer

Answer: (b) 3.9%


Question 24.
The half-cell reactions for rusting of iron are
2H+ + \(\frac {1}{2}\) O2 + 2\(\bar{e}\) ? H2O, E° = + 1.23 V
Fe2+ + 2\(\bar{e}\) ? Fe (s), E° = – 0.44 V
?G° (in kj) for the reaction is
(a) -76
(b) -322
(c) -122
(d) -176

Answer

Answer: (b) -322


Question 25.
An aqueous solution containing one mole per litre of each of Cu(NO3)2, AgNO3, Hg (NO3)2 and Mg (NO3)2 is being electrolysed using inert electrodes. The values of standard electrode (reduction) potentials in volts are Ag/Ag+ = + 0.80, Hg/ Hg2+ = 0.79, Cu/Cu2+ = 0.34, Mg/Mg2+ = -2.37.
With increasing voltage, the sequence of deposition of metals on cathode will be
(a) Ag, Hg, Cu, Mg
(b) Mg, Cu, Hg, Ag
(c) Ag, Hg, Cu
(d) Cu, Hg, Ag
(e) Cu, Hg, Ag, Mg.

Answer

Answer: (c) Ag, Hg, Cu


Question 26.
MCQ Questions for Class 12 Chemistry Chapter 3 Electrochemistry with Answers 1
calculate ?\(_{HOAc}^{?}\) using appropriate molar conductance of the electrolytes listed above at infinite dilution of H2O at 25°C.
(a) 517.2
(b) 552.7
(c) 390.7
(d) 217.5

Answer

Answer: (c) 390.7


Question 27.
The highest electrical conductivity of the following aqueous solutions is of?
(a) 0.1 M acetic acid
(b) 0.1 M chloro acetic acid
(c) 0.1 M fluoroacetic acid
(d) 0.1 M difluoro acetic acid

Answer

Answer: (d) 0.1 M difluoro acetic acid


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